1. Field of the Invention
The present invention relates to a shape measurement device.
2. Background Art
Heretofore, a shape measurement device has been known, which scans a surface of a work, that is referred to as an object to be measured, by a probe in a noncontact manner, and measures a shape of the surface of the work (for example, refer to Japanese Translation of PCT International Application Publication No. JP-T-2009-534969).
The probe is composed by including an imaging element such as a charge coupled device (CCD) and a complementary metal oxide semiconductor (CMOS), an image-forming lens, a line laser, and the like, and performs the measurement by using the Scheimpflug principle.
As shown in FIG. 6, the Scheimpflug principle refers to that, in the case where planes, which are obtained by individually extending an imaging plane of the imaging element, a principal plane including a principal point of the image-forming lens, and an irradiation plane of the line laser irradiated onto the work, are arranged so as to intersect one another at one point, the imaging plane of the imaging element entirely turns to a focusing state.
In the probe using the Scheimpflug principle as described above, measurement accuracy (resolving power) and a measurement range are in a tradeoff relationship. That is to say, in the case of measuring, by the imaging element, the work placed on the irradiation plane of the line laser, then an imaging range of the image-forming lens for use is decided by optical magnification thereof.
Therefore, as shown in FIG. 7, in the case of measuring a wide range, an image-forming lens of low magnification is used, and in the case of measuring a narrow range with high accuracy, an image-forming lens of high magnification is used.
Incidentally, heretofore, in the probe as described above, a configuration has been adopted, in which the line laser and the image-forming lens are fixed to the probe concerned in a manufacturing process, and cannot be replaced once being fixed. Therefore, the measurement accuracy and measurement range of the probe have been uniquely decided by optical magnification of the fixed image-forming lens and a size of the imaging element.
Therefore, in matching with a size of the work for which the measurement is desired to be performed, it has been necessary to switch a probe having an appropriate measurement range (or measurement accuracy), and it has been necessary to prepare plural types of probes different in specifications of the measurement range (measurement accuracy).
In order to prepare plural types of the probes only because desired measurement ranges (measurement accuracies) differ, enormous cost has occurred, and in addition, it has been necessary to perform an alignment operation and the like every time of exchanging the probe, resulting in an increase of installation man-hours.